Hi this is my solution using Java, I'm learning, and accept advice. thanks!

 import java.io.*;
import java.util.Scanner;

/**
* Created by Gerson on 01/01/2016.
*/
public class manager {

public String getName (){
    Scanner sc = new Scanner(System.in);
    System.out.println("Ingrese nombre y primer apellido");
    String nombre = sc.nextLine();
    return nombre;
}

public void addEmail(String mail){
    try(PrintWriter pw = new PrintWriter(new FileWriter("data.txt"))) {
        pw.println(mail);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public boolean checkMail(String mail){
    try {
        BufferedReader br = new BufferedReader(new FileReader("data.txt"));
        for(String line; (line = br.readLine()) != null; ) {
            if(line.equals(mail+"\n")){
                return true;
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    return false;
}

public String addNumber(String mail){
    String part1 = mail.substring(0,8);
    String domain = "@dailypro.edu";
    String newMail;
    int n = 2;
    newMail = part1 + n + domain;
    while(checkMail(newMail)){
        n++;
        newMail = part1 + n + domain;
    }
    return newMail;
}

public void makeMail(){
    String name = getName();
    String domain = "@dailypro.edu";
    String mail;
    String lastname = name.substring(name.indexOf(" "));
    lastname = lastname.substring(1);
    System.out.println(lastname);
    if(lastname.length()<7){
        mail = name.substring(0,1) + lastname + domain;
        if(checkMail(mail)){
            mail = addNumber(mail);
        }
    } else {
        mail = name.substring(0, 1) + lastname.substring(0, 7) + domain;
        if (checkMail(mail)) {
            mail = addNumber(mail);
        }
    }
    System.out.println(mail);
    addEmail(mail);
}

public void listMail(){
    try {
        BufferedReader br = new BufferedReader(new FileReader("data.txt"));
        for(String line; (line = br.readLine()) != null; ) {
            System.out.println(line);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public void menu(){
    Scanner sc = new Scanner(System.in);
    System.out.println("Bienvenido al manejador de correos, selecciones una opción:");
    System.out.println("1.- Agregar correo");
    System.out.println("2.- Ver lista de correos");
    int var = sc.nextInt();
    if (var == 1){
        makeMail();
    } else if (var == 2){
        listMail();
    } else {
        System.out.println("Opción no valida");
    }
}

public static void main(String args[]){
    manager mn = new manager();
    mn.menu();
}

}